Today, microprocessor-based personal computers (PCs) find wide application in education, science, business and the home. As the use of personal computers becomes more widespread, the demand for faster and more flexible video features has also expanded. Consequently, computer manufacturers are diligently searching for ways to increase the performance and adaptability of video display systems while reducing the cost to the consumer.
In general, the internal architecture of the personal computer is organized such that the central processing unit (CPU) is housed on a printed circuit board which also contains system memory and supporting logic devices. This board is commonly referred to as a "motherboard". In the past, if users desired video graphics features, they necessarily had to purchase a separate video card which was designed to be plugged into a slot coupled to the motherboard across a connective bus interface. This card would contain dual-ported video random-access memories (VRAMs) which would be used to store the video display data later output to the display device (i.e., a monitor). The video card would have its video timing circuitry configured for a particular type of monitor; that is, the card could only be used with that type of monitor and no other. This past approach was typical of machines such as the original Macintosh II series computers, and is still in wide use today.
The use of a separate video card, however, has several important disadvantages, perhaps the most fundamental limitation being that the user either needs a different video card for each type of display or monitor that the computer is connected to, or must somehow reconfigure the system (e.g., by flipping various selection switches) when changing monitors. For example, a computer utilized to produce an image on a 15-inch portrait color monitor requires one type of video card, while one coupled to a 9-inch Black and White screen requires a different card. Thus, different monitors require matched video cards which ultimately reduce the flexibility afforded the user.
As will be seen, the present invention obviates the need for different video circuitry, in the form of a separate video card or otherwise, associated with each type of monitor to which the computer is connected. Thus, a variety of monitor types may be employed without reconfiguring the internal video circuitry of the computer.
The present invention accomplishes this by the use of self-configuring video circuitry which first identifies the type of monitor being used, and then selects one of a plurality of parameter sets corresponding to the type of monitor being used. These parameters are then supplied to the rest of the display circuitry. The present invention, therefore, permits connection to a variety of monitors without the need to replace any video circuitry. Ultimately, this results in greater convenience for the user, since there is no need to change cards, flip selection switches, or re-configure the computer system when changing monitors.